LR3 V6 300,000 Miles
I took the LR to the dealership some time back to have the crankshaft sensor replaced, while I was there I asked them to investigate why I had surging revs while maintaining 30-40 MPH and accelerating in 2nd and 3rd gear. They fixed my sensor and told me I need a new transmission. Only now is it getting to where this issue is really bothering me, so the other day I asked for a full maintenance history to see if they had any info on previous transmission service/fluid changes. Unfortunately they had recently purged their records and could only provide 2 years of history on the vehicle. It did however show the comments on the diagnostic that I asked for not too long ago: "TORQUE CONVERTER LOCK UP. NEEDS NEW TRANNY"

Okay. So maybe I don't need a whole new transmission. Yesterday I took the crossmember out and collected a small sample of the oil through the drain plug (the fill plug is impossible to turn) and while a little dirty it was certainly not burned and there was nothing suspect inside it.

Symptoms:
Surging revs in D accelerating and maintaining speed 15-45 MPH
In manuel selection mode I can almost completely contain the surging to second gear
There are no symptoms if accelerating quickly/driving aggressive
There are no symptoms until the vehicle warms up
No related codes are being thrown (I have an O2 sensor that needs replacing)

If anybody has any experiences with this sort of problem I would sincerely appreciate learning about them. I'm going to take it to a friend next week as he has better diagnostic equipment.

 

A GAP IIDTool would help you diagnose whats going on inside the transmission. You can actually watch each solenoid amperage change as the transmission shifts through the gears. It's easy to see if any are acting different or malfunctioning which is not uncommon on the ZF trans. My converter would not go into lockup and I had a raise in rpm when shifting to 3-4. I replaced the shift solenoids on the valve body and both issues vanished. If it were me, I'd perform a trans filter and fluid change and while in there I'd replace all of the solenoids and the mechatronic pass through bulkhead. If you got 300K on it that transmission doesn't owe you a nickel, so putting a few dollars in it has to be considered maintenance at this point. 300k? really? That's amazing.
V6 sohc... have you replaced the cam chain cassettes and EGR yet? (maybe a few times?)

 

You're doing well to get 300k out of the trans, doesn't sound terminal yet so above advice is solid.

 

Looking at the workshop manual it states that I need a special tool to get the valve body out, is this actually the case or will something more standard work okay? Also any tips about removing it would be much appreciated.

 

No special tools needed to remove the valve body, just a few torx bits. No need to loosen or remove the shift cable or lever. Take a couple pictures of the valve body while still installed. Key on the position of the plastic slide and the spool it moves for reference when you reinstall the valve body. There is a youtube video where the valve body is being removed. Search ZF 6HP26 rebuild. Your going to need to drop the exhaust from the manifolds and remove the trans crossmember to gain access to a few pan bolts. I would guess the workshop manual will have most of the procedure documented. There is a fair amount of info out there on repairs and maintenance. Just run a search and you'll likely find any info you need. Make sure you order a new foam insulating strip for the solenoids.

 

Update

I took it up to a friend of mine who runs a Foreign/Domestic tranny shop and has some experience with this transmission, we hooked it up and drove around for a bit, he confirmed the diff was locking but all solonoids were acting normally, and there was nothing obvious actually wrong with it from the computers point perspective (except the temp sensor showed -40, obviously that needs fixing.) He advised that I check fluid level so I took the crossmember out again and after finally forcing the fill plug open I added 1.75 quarts of fluid on level ground at idle. It doesn't seem to have made a difference yet but I'll give it some time to work before I start tearing into the valve body to check for blockages. I'm expecting a full rebuild/replace but I'd like to get as many miles out of it as I can.

 

Your statement: "I'd like to get as many miles out of it as I can" Sounds like you already have, my friend.

 

I hope you didn't just shove extra fluid in there
Did you go through the proper refill procedure, getting the correct slow drip at the correct trans fluid temp?

 

I followed proper checking and filling procedure, yes. Upon closer inspection I believe I have several points of oil and transmission fluid leakage, very slow, that will require some significant work. I am on the lookout for a parts vehicle to purchase.

 

Update: After adding transmission fluid the symptoms have completely disappeared in M/S mode when shifting manual, however symptoms remain on all automatic modes. All readings from the computer, including solenoid voltages are completely normal. Had a friend who works on ZF transmissions regularly look as well, he hooked up and got completely normal readings as well.